Thrust-controlling apparatus with variable axial flow area for differing flight regimes and thrust reversal

ABSTRACT

Apparatus includes shroud positioned at rear or jet nozzle to surround and control gas stream. Shroud includes forward fixed section secured to engine at outlet flange or tailpipe and aft section axially movably mounted to fixed section. In stowed position aft section cooperates with forward section to define shroud as substantially imperforate conduit in continuation outlet or tailpipe. In deployed position, one or more gaps are formed between forward end of aft section and rearward end of forward section for reverse thrust gas flow. Diversion plug coaxial with shroud varies axial flow area for differing flight regimes. Swingable flaps or blades form trailing edge of aft section and vary shape of outer wall. Blades and plug are operable independently to produce all necessary outlet combinations. For reverse thrust, plug is expanded and aft section deployed. Blocker doors on inner wall of aft section are caused to swing into engage-expanded plug and block axial rearward flow of gas, forcing it through reverse thrust openings.

iJnited States Pater [72] lnventors Richard 111. Timms San Diego;Leonard Holman, Imperial Beach, both of Calif.

[21] Appl. No. 887,061

[22] Filed Dec. 22, 1969 [45] Patented Oct. 12, 19711 [73] Assignee RohrCorporation Chula Vista, Calif.

[54] THRUST-CONTROLLING APPARATUS WITH VARHABLE AXIAL FLOW AREA FORDIFFERIING FLIGHT REGLMES AND THRUST REVERSAL 20 Claims, Drawing Figs.

[52] US. Cl ..239/265.29,

[51] lint. Cl 864: /06

[] Field of Search ..239/265,13,

[56] References Cited UNITED STATES PATENTS 2,933,890 4/1960 Morrison239/265.3l

2,952,124 9/1960 Pearson... 239/265.l3

3,347,467 10/1967 Carl et a1. 239/265.13 X

Primary Examiner-M. Henson Wood, Jr. Assistant Examiner.lohn J. LoveAttorney-George E. Pearson ABSTRACT: Apparatus includes shroudpositioned at rear or jet nozzle to surround and control gas stream.Shroud includes forward fixed section secured to engine at outlet flangeor tailpipe and aft section axially movably mounted to fixed section. Instowed position aft section cooperates with forward section to defineshroud as substantially imperforate conduit in continuation outlet ortailpipe. ln deployed position, one or more gaps are formed betweenforward end of aft section and rearward end of forward section forreverse thrust gas flow. Diversion plug coaxial with shroud varies axialflow area for differing flight regimes. Swingable flaps or blades formtrailing edge of aft section and vary shape of outer wall. Blades andplug are operable independently to produce all necessary outletcombinations. For reverse thrust, plug is expanded and aft sectiondeployed. Blocker doors on inner wall of aft section are caused to swinginto engage-expanded plug and block axial rearward flow of gas, forcingit through reverse thrust openings.

104 30 as 17s 33 196 200 a 60 PATENTED UEHZIQH 3612MB SHEET 2 GF 3VNVENTOR,

RICHARD H. TIMMS LEONARD HOLMAN ATTORNEY PATENTfiflucnzlsn 3,612 402SHEET 3 0F 3 INVENTOR.

RICHARD H. TIMMS LEONARD HOLMAN THRUST-CONTROLLING APPARATUS Wll'lllliVARIABLE AXTAL FLOW AREA FOR DIFFERJING FLTGIHIT RlEGllMlES AND THRUSIREVERSAIL BACKGROUND OF THE INVENTION This invention lies in the fieldof gas turbine engines, more commonly called jet engines, which producereaction thrust by ejecting a high-velocity stream of gas from theexhaust nozzle of the gas turbine. Airplanes driven by jet engines flyand land at much higher speeds than propeller-driven aircraft. Theirhigh-landing speed puts a great burden on the wheel brakes and of coursethey do not have propellers which are readily reversible to producereverse thrust. Therefore it is necessary to provide apparatus toreverse the gas stream to accomplish this result.

It is also highly desirable to be able to control effective thrust inflight. This is particularly so in the case of tactical militaryairplanes, which may be required to decelerate rapidly in combatmaneuvers or limit their speed in steep dives in bombing operations.Conventionally, speed brakes are used for this purpose.

Various types of thrust reversers have been in use for many years,primarily to reduce landing run, although some have been successfullyused in flight to reduce forward speed more rapidly than by throttlingthe engine. All of them utilize a basic principle of blocking therearward flow of the exhaust gas stream and diverting it laterally. Ifthe stream has no forward component it will act in the manner of a speedbrake by interference with the free airstream. Normally, however, thestream is directed substantially forwardly to produce an actual reversethrust. One common type uses a pair of deflectors which meet externallybehind the nozzle to divert the stream laterally in opposite directions,usually with a forward component. Another similar type has doors mountedwithin the nozzle to block flow, lateral openings in the nozzle, anddoors or deflectors which normally cover these openings, but may beswung outward to uncover the openings and direct the diverted streamslaterally and forwardly. In another type, doors within the nozzle may bemoved to block flow, and cascade passages are uncovered in the sidewallsto allow the gas to issue laterally and forwardly.

All of these systems work reasonably well but they have variousdrawbacks. They are difficult to modulate and normally are used only infully deployed position. The external target type, with deflectorsbehind the nozzle, requires considerable supporting structure andusually has larger deflectors than is desirable. Also, it is difficultto arrange a pivotal mounting which will make them fail-safe; i.e.,mounted so that in the event the actuating mechanism fails they will beurged by the gas stream toward stowed position. The other types haverather complicated mechanism which is subject to possible trouble orfailure.

It is also highly desirable, particularly in military airplanes, to beable to vary the exit throat area through a wide range and also to beable to vary the total shape of the outlet through a wide range ofconvergent and convergent-divergent forms. Attempts to combine theserequirements with suitable thrustreversing means have not so far metwith outstanding success. One example of such variable throat mechanismis disclosed in Glass US. Pat. No. 3,391,869, which is assigned to theassignee of the present invention.

SUMMARY OF THE INVENTION The present invention provides apparatus whichaccomplishes all of the functions mentioned above in a relatively simplemanner and with a high degree of dependability. The shape of the thrustgas outlet of a jet engine can be varied for all conditions from takeoffto supersonic flight with afterbumer, and thrust reversal can be fullymodulated for various flight conditions as well as for landing roll.

Generally stated, the apparatus includes a shroud having a forwardsection fixedly connected to the engine and an aft section axiallymovably mounted to the forward section. When the aft section is stowed,it cooperates with the forward section to define the shroud as asubstantially imperforate conduit, coaxial with the outlet or tailpipeof the engine and acting as a continuation thereof.

When the aft section is deployed rearwardly, one or more gaps are formedbetween the formerly adjacent edges of the forward and aft sections andthese gaps define lateral flow paths through the shroud wall for theexhaust gas which is blocked from rearward flow. The adjoining edges ofthe sections may lie in a single transverse plane if it is desired toprovide a complete annular reverse thrust opening.

A diversion plug is located coaxially in the shroud and has a generallystreamlined form, the intermediate portion of said plug being expandableand contractable to vary the outlet area at the throat zone. Thetrailing edge portion of the aft shroud section is made up of aplurality of circumferentially arranged flaps or blades pivotallymounted at their forward edges to the fixed part of the aft sectionsubstantiaflly at the throat zone when the aft section is stowed. Thelateral margins of the blades engage each other in sliding sealedrelation and the blades swing in unison toward and away from the axis ofthe shroud to vary the exit cone. The control of the blades isindependent of the control of the plug and thus it is possible toachieve a wide range of outlet configurations for differing flightregimes.

Thrust control is achieved by expanding the plug to a predetermineddegree and deploying the aft shroud section to a predetermined extent.As the shroud moves rearwardly, a plurality of blocker doors swinginwardly toward the plug. Since the controls are separate, any degree ofblocking can be attained. This is particularly valuable in controllingthe diving maneuvers of combat airplanes. For maximum thrust reversalduring ground roll, the plug is fully expanded and the aft shroudsection is fully deployed, causing the blocker doors to movesubstantially into contact with the expanded plug and prevent anyrearward flow of gases so that they must all pass through the reversethrust openings.

BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages and featuresof novelty will become apparent as the description proceeds inconjunction with the accompanying drawings, in which:

FIG. 11 is a schematic side elevational view, partly in section, showingthe total apparatus in one preferred form;

FIG. 2 is a schematic partial sectional view taken on line 2- 2 of FIG.1 with the aft shroud section in the deployed position indicated by thebroken lines;

FIG. 3 is a schematic partial sectional view taken on line 3- 3 of FIG.11;

FIG. 4 is a schematic partial plan view taken on line H of FIG. 1; and

FIG. 5 is a schematic side elevational view, partly in section, of amodified form of blocker door operating mechanism.

DESCRIPTION OF PREFERRED EMBODIMENTS The thrust-controlling apparatus ofthis invention may be used with any conventional engine installationwhether wing or fuselage mounted, and operates in the same way in all instances. For convenience of illustration it is shown in FIG. 1 asmounted coaxially directly aft of the engine outlet or tailpipe Ml. Theshroud 112 includes a forward section M fixedly secured to the engineand with its leading edge 16 in direct, sealed contact with the engineor tailpipe flange l8. Shroud 12 further includes an aft section 20 indirect continuation of the forward section and axially movably mountedthereto by means to be detailed later. When the aft section is in stowedposition, as indicated by solid lines, it cooperates with the for wardsection to define the shroud as a substantially imperforate conduitforming a direct coaxial continuation of the nozzle and acting tosurround and control the exhaust gas stream issuing from the nozzle.

The forward shroud section 14 is provided with an annular trailing edge22 having a face 24 which converges rearwardly and serves as the forwardwall of a lateral passage through the shroud when the aft shroud sectionis deployed. The leading edge 26 of the aft section is provided with acorresponding face 28 which forms the rear wall of the lateral passageon deployment. Because of the rearwardly converging surfaces, theexhaust gas which exits therebetween when the aft section is deployedwill have a forward component of about 45 to produce a very high degreeof reverse thrust. In some cases a full annular opening is desired, andfaces 24 and 28 are full annuli. Seal member 30, carried by leading edge26, contacts surface 24 to prevent escape of exhaust gas during normalflight.

There are many installations where it is preferable to provide aplurality of arcuate lateral openings separated by shielded portions toprevent discharge of gas against structural elements. For this purposethe shroud is modified at a plurality of areas around the circumference,one of which is illustrated in the upper portion of FIG. 1. ConsideringFIGS. 1 and 2, it will be seen that an arcuate portion of leading edge26 is extended forwardly to serve as a blanking panel 32 which isaxially movable in a recess 34 in the outer wall of section 14. Thisblanking panel is a structural member integral with the main body of aftsection 20 and is provided with a guide 36 which slides axially on track38 fixedly secured to section 14. The track and guide provide thesliding support of aft section 20 on forward section 14. Recess 34 isprovided with a cover plate 40 which overlies the forward part of theblanking panel, and a seal member 42 carried by leading edge 26 engagesthe aft edge of the cover plate. Suitable sealing means may also beprovided along the lateral edges of the blanking panel if desired.

The aft shroud section is moved between stowed and deployed position bymechanism including an actuator 44, such as an electric motor, connectedthrough gearbox 46 to a drivescrew 48. The latter extends axially in achannel 50 formed in the blanking panel and is in driving engagementwith a nut 52 which is fixedly mounted in the forward end of thechannel. There is one such complete mechanism (except the actuator) foreach of the blanking panels spaced around the periphery of the shroudand synchronism between the drives is maintained by a flexible driveshaft 54 connected between the several gearboxes. The motor is fullycontrollable to position the aft section 20 at any point along its pathof travel.

The shroud is a continuation of the nozzle outer wall. In order to varyits exit area and cone of convergence, the trailing portion 56 of aftsection 20 comprises a plurality of circumferentially arranged flaps orblades 58, each connected at its leading edge 60 to a pivotal mounting62 so that each blade can swing toward and away from the axis of theshroud. Referring to FIG. 3 which shows the blades in expanded positionin solid lines and in contracted position in broken lines, it will beseen that each blade 58 is formed as an elongate hollow box with leaves64 and 66 forming extensions of its lateral edges. The leaves 64 of oneblade slide within the leaves 66 of the adjacent blade to provide forvariation of the angle of convergence while maintaining an imperforatewall to prevent leakage of gas between the blades.

All of the blades 58 are swung inward and outward in unison by themechanism illustrated in the lower portion of FIG. 1. This mechanismincludes an actuator such as an electric motor 68 and a gearbox 70,mounted between the inner and outer walls 72 and 74 of the forwardshroud section 14. A shaft 76 driven by the gearbox extends rearwardthrough suitable openings in faces 24 and 28, terminating in a splinedportion 78. The shaft is slidably mounted within a tube 80 rotatablymounted in bearings 82 and 84 for translation with the aft section 20.The tube is internally splined throughout its length so that it maytranslate with respect to shaft 76 while being rotatably driven by thesplined connection at any point of translation, thus constituting it avariable length force transmitting means.

Rearward of bearing 84, the tube is united to drivescrew 86 which isthreaded through nut 88 fixedly mounted within aft section 20 andterminates in'a rotatable but nonsliding connection 90 with the axiallymovable actuating ring 92. It will be apparent that rotation ofdrivescrew 86 in nut 88 will produce axial movement of ring 92 whichextends annularly between the inner and outer walls 94 and 96 of the aftsection 20. Link 98 is pivotally connected to the ring at 100 and toblade 58 at 102 to swing the blade angularly in response to translationof the ring. There is a complete drive mechanism (except the actuator)at each location around the periphery where there is a blanking paneland synchronism is achieved by the use of flexible drive shafts 104connecting the gearboxes.

An expandable and contractable diversion plug 106 serves as a nozzleinner wall and a means to vary the throat area. It also cooperates withthe shroud to establish varying degrees of nozzle convergent anddivergence and to produce varying degrees of thrust reversal. Ingeneral, it includes a forward cone section 108 diverging rearwardly andan aft cone section 110 diverging forwardly, and is provided with atapered nose member 112 and a tapered tail member 114 giving the totalplug a streamlined configuration. The bases 116 and 118 of the conesmeet in a plane transverse to the axis of the shroud adjacent to theplane defining the throat zone. The bases could meet directly at thethroat zone, but the aft cone section is extended slightly forwardthereof as shown for streamlining purposes. Thus the throat zone isactually in the plane of maximum diameter of the aft cone section. Itwill be noted that the pivotal mountings 62 for blades 58 aresubstantially in the plane of the throat zone when aft shroud section 20is stowed. This location facilitates formation of the various outletconfigurations necessary for differing flight regimes.

To achieve a substantially smooth conical surface at all stages ofexpansion, each of said cone sections is constructed substantially inthe manner illustrated in FIG. 3 which shows a portion of the aft conesection. The cone is made up of a plurality of fore and aft extendingelongate petals 120 and 122 respectively reinforced by box or hatsections 124 and 126, the petals 120 lying inwardly adjacent to petals122 and ar ranged in sliding contact in all stages of expansion toprovide a seal against leakage of gas. Petals 120 are angularly bentalong their centerlines and petals 122 are arcuately curved, theassembly providing a generally circular cross section at any transverseplane.

Returning to FIG. 1, it will be seen that all of the petals 120 and 122are pivotally connected at a circumferential series of pivot points 128to a collar 130. Petals 132 of the forward cone section 108 aresimilarly connected at 134 to a collar 136. Each set of one forwardpetal and one aft petal are pivotally connected at their base ends by apivot pin 138 substantially in the plane of the throat zone.

The supporting and operating structure for plug 106 comprises asupporting tube 140 located coaxially within the shroud, a spacer ring142 at the forward end of tube 140, and a second tube 144 extendingforward of the spacer ring and rigidly secured to the inner ends of aplurality of circumferentially spaced hollow struts 146, the outer endsof which are rigidly secured to the inner wall 72 of the forward shroudsection 14. The tapered nose member 112 is in turn rigidly secured totube 144 with its aft end slightly spaced radially outward of theforward end of cone section 108.

Coaxially located within supporting tube 140 is an actuator comprising acylinder 148 connected to bracket 150, a piston, not shown, and a pistonrod 152 extending from the forward end of the cylinder, the actuatorbeing operable in known manner. A force transfer member 154 is mountedat the free end of the piston rod and a plurality of actuator links 156are connected at their forward ends to member 154 by pivot pins 158 andare connected at their aft ends to a sliding collar 160 by pivot pins162.

The sliding collar 160 forms a part of a straight line motion linkagewhich includes a first link 164 pivotally connected at its inner end tocollar 160 at 166 and pivotally connected at its outer end to a set ofpetals, 122, 1132 at 139. A second, shorter link 179 is pivotallyconnected at its inner end to fixed collar M2 at 1179 and is pivotallyconnected at is outer end to an intermediate point 169 of link 169. Thelengths of links 1164 and 1179 and the point of attachment 1169 are sochosen that as collar 1169 slides forward link 1179 will constrain theouter end of link 1641 to move radially inward in substantially astraight line in the transverse plane of the throat zone, carrying withit the petals 1122 and 1122.

There are a plurality of these straight line motion linkages spacedperipherally around collars 1169 and 1172, each moving in a planecontaining the axis of the shroud, and they all move in unison to expandand contract the bases of the cone sections. The change in the basediameters changes the heights, or axial lengths, of the cone sectionsand accordingly collars 1139 and 1136 are slidingly mounted on tube M9and spacer ring M2 to accommodate the variation. While nose member 11112is fixedly mounted on tube 1M, tail member 1114 is directly connected tocollar 139 and moves axially with it.

As previously pointed out, the controls for the plug 196 and the blades59 are independent. Therefore the plug may be moved to any stage ofexpansion with blades 59 remaining set, and the blades may be moved toany degree of convergence with the plug remaining set. Consequently thetwo may be relatively arranged to define any degree of convergent orconvergent-divergent outlet configuration for all types of operationfrom takeofi to supersonic flight with afterbumer.

For modulated or complete thrust reversal the aft shroud section 29 isdeployed rearward to the desired extent in the manner previouslydescribed, partially or fully opening the lateral flow paths through thewall of the shroud. in order to block rearward flow and redirect the gasthrough the lateral openings, blocker doors 1176 are provided adjacentto the leading edge of aft cowl section 29. A series of these doorsextends completely around the inner wall.99, each being set in a recessan pivoted at its leading edge to bracket 1179 at 199. The arrangementand planfonn of the doors is shown in P16. 4, where it will be seen thattheir leading edges 192 form a substantially continuous ring while theirlateral edges 1194 are tapered. With this configuration edges l willjust touch each other as their trailing edges 196 contact the surface ofthe plug, thus completely blocking axial rearward flow of the exhaustgas stream.

The means for actuating the blocker doors includes a track 1188 fixedlysecured to the structure of forward shroud section M and extendingrearwardly through suitable openings in faces 24 and 29 into the aftsection. An actuating ring 1199 is slidable on track 1199 between limitsset by contact with stop members 192 and 1194 on the track. initialrearward movement of section 29 carries the ring rearward until itcontacts stop member 1941, and section 29 then moves rearwardly withrespect to the ring. Link 196 is connected at its forward end to anintermediate point on door 1176 by pivot pin 199 and is connected at itsaft end to ring 1199 by pivot pin 299. The relative forward movement ofring ll99 during the later stage of deployment of section 29 appliesaxial force along the length of link 1196 to move the door to itsdeployed position shown in broken line in contact with or immediatelyadjacent to the surface of the expanded plug. Reverse movement allowsthe doors to return to stowed position. in the event of failure of thedeployment mechanism for section 29, the gas force on the door acts toreturn the door and section 29 to stowed position, providing fail-safe"capability. it will be understood that ring ll extends around thecircumference of section 29 between inner and outer walls 94 and 96 andis carried by a plurality of tracks ll99. A link 1196 is provided foreach door.

Since plug 1196 is located directly in the path of the exhaust gas atall times it is desirable to provide a cooling system. Cooling air fromthe engine fan or other source passes rearwardly between the dual wallsof nozzle 119, then between the walls of section 12 through struts M6into tube 11M, where it passes forwardly into nose member 1112 andrearwardly into tube M9 and around the actuator. it then passesrearwardly over the interior and exterior surfaces of the cone sections.As a result, all portions of the plug are maintained at a tempera turemuch lower than that of the exhaust gas.

A modified form of actuating mechanism for the blocker doors isillustrated in H6. 5, this mechanism providing for graduated movement ofthe doors throughout the movement of aft shroud section 29, the openingof the lateral flow paths always being sufficient to compensate for thereduction of open area at the throat zone. in this form, the operatingmechanism for moving the aft shroud section 29 and the blades 59, aswell as the expandable plug 196, is the same as in the form previouslydescribed.

A blocker door 292 is located in a recess in the inner wall 99 of theaft shroud section 29 adjacent to the leading edge 294 and is pivotedslightly behind its own leading edge 296 on bracket 299 by means ofpivot pin 219. When the door is fully deployed, it inner surface is inalignment with angled face 292 of leading edge 294 to form the rear wallof the lateral opening for reverse thrust flow. An actuating means inthe form of an abutment ring 2114 is located between walls 94 and 96 butis fixedly connected by suitable structure to the forward shroud section12 so that it is relatively movable forwardly from the solid lineposition with respect to the aft shroud section 29 when the latter movesrearwardly toward its deployed position.

A pair of toggle links 236 and 2119 are: arranged in generally fore andaft relation and are pivotally connected to each other by pivot pin 229.Link 2116 is generally straight while link 219 is generally L-shaped sothat when it lies against outer wall 96 the ends of the links and theirpivotal connection will not be in alignment. Link 216 is connected tobracket 222 by a pivot pin 22 i and link 2119 is connected to abutmentring 2119 by pivot pin 226. A drive link 229 is connected at one end todoor 292 by pivot pin 239 and is connected at its opposite end to link216 by pivot pin 232.

When section 29 is deployed rearwardly, it carries bracket 222 backtoward stationary abutment ring 2114. Since pivot 229 is not in linewith pivots 224 and 226, the toggle linkage will break upwardly as seenin the figure. Thus, link 2ll6 will swing counterclockwise and applyforce along the length of drive link 229 which in turn will swing door292 toward its deployed position. There is no lost motion in any part ofthis mechanism so door 292 will move generally proportionally withmovement of section 29 and will arrive at the broken line position justas section 29 is fully deployed. Since the lateral flow openingcommences to enlarge immediately and the door has little effect in itsinitial movement, the lateral opening will always overcompensate for thereduction of area at the throat zone.

It will be understood that a series of blocker doors extends completelyaround the periphery of section 29 as in the previous form and thatthere is a toggle linkage mechanism associated with each door. Also, asin the previous form, gas pressure on the doors acts in a fail-safemanner to return the doors and aft shroud section to stowed position inevent of mechanical failure.

What is claimed as new and useful and desired to be secured by US.Letters Patent is:

ll. Thrust controlling apparatus for use in combination with a jetengine having a rearwardly discharging exhaust outlet or tailpipe,comprising: a shroud carried by said engine and located rearwardly ofthe exit end of said outlet or tailpipe and coaxial therewith tosurround and control the exhaust gas stream issuing from said outlet ortailpipe; and a streamlined diversion plug mounted coaxially within theshroud to define the inner wall of the flow path for the exhaust gasstream; the intermediate portion of the plug being expandable andcontractable to vary the flow path area for differing flight regimes;said shroud including means to provide lateral flow path means throughits wall and means to coact with the expanded plug to block rearwardflow of the exhaust gas stream and redirect it through the lateral flowpath means to produce reverse thrust.

2. Apparatus as claimed in claim 1; said shroud including a fixedforward section and an aft section axially movably mounted on theforward section and adapted in its stowed, forward position to cooperatewith the forward section to define said shroud as an elongatesubstantially imperforate conduit; said aft section being movablerearwardly to a deployed position in which at least part of its forwardend is spaced rearwardly from the rearward end of the fixed section todefine said lateral flow path means through the wall of the shroud.

3. Apparatus as claimed in claim 2; the means to coact with the expandedplug comprising a series of peripherally arranged blocked doorspivotally mounted to the inner wall of the aft section of the shroudsand swingable into engagement with the expanded plug; said doors beingformed and arranged to completely close the rearward flow path in fullydeployed position.

4. Apparatus as claimed in claim 3; said doors being provided withlinkage means adapted to cause their deployment and stowage in responseto movement of the aft section to deployed and stowed positions.

5. Apparatus as claimed in claim I; the intermediate portion of saidplug comprising a forward cone section diverging rearwardly and an aftcone section diverging forwardly; the bases of said cone sectionsmeeting in a plane transverse to the nozzle axis and defining a throatzone of variable area.

6. Apparatus as claimed in claim 5; the trailing portion of the aftshroud section comprising a plurality of circumferentially arrangedblades, each connected at its forward edge to a pivotal mounting on theaft shroud section; said pivotal mountings, when the aft shroud sectionis in stowed position, lying in said transverse plane at the throatzone; and means to swing said blades in unison to selected angularpositions independent of the condition of expansion of the diversionplug to modify the shape of the outer nozzle wall for differing flightregimes.

7. Apparatus as claimed in claim 6; the lateral margins of said bladeshaving sealing means in slidable engagement with adjacent blades toproduce a substantially imperforate continuation of the outer nozzlewall in all positions of adjustment.

8.-Apparatus as claimed in claim 1; the intermediate portion of saiddiversion plug comprising a forward cone section diverging rearwardlyand an aft cone section diverging forwardly; the bases of said conesections meeting in a plane transverse to the nozzle axis and defining athroat zone of variable area; a first support member at the forward endof said forward cone section; said forward section comprising aplurality of fore and aft extending elongate petals arranged inlaterally overlapping and sliding relation; said petals being pivotallymounted at their forward ends on said first support member; a secondsupport member at the aft end of the aft cone section; said aft sectioncomprising a plurality of petals similar to those of the forward sectionand pivotally mounted at their aft ends to the second support member; aperipherally arranged series of straight line motion linkages located inthe general transverse plane of the throat zone and each having an outerfree end movable radially in said plane; the adjacent ends of the petalsof the forward and aft cone sections being pivotally connected in pairsto the outer free ends of said linkages to move radially therewith andvary the base diameters of the cone sections; and means to actuate allof said linkages in unison.

9. Apparatus as claimed in claim 8; said first and second supportmembers being axially movable to provide for changes in the axiallengths of the cone sections in response to changes in their basediameters.

10. Apparatus as claimed in claim 9; a fixedly mounted tapered nosemember extending forwardly ahead of the forward cone section; and atapered tail member extending rearwardly of the aft cone section andmounted on said second support member for axial movement therewith.

11. Apparatus as claimed in claim 8; including a plurality ofperipherally spaced radially extending struts within said shroud andhaving their outer ends fixedly secured to the inner wall thereof at itsforward end; and elongate support tube arranged coaxially in said shroudand fixedly secured at its forward end to the inner ends of said struts;said support members comprising rings axially slidably mounted on saidtube; saidstraight line motion linkages being mounted on the outer wallof said tube intermediate its ends; said means to actuate said linkagesbeing mounted within said tube; and actuator links connecting saidactuating means to said linkages.

12. Apparatus as claimed in claim 8; including an elongate support tubefixedly mounted coaxially in said shroud; a first ring fixedly mountedon said tube; a second ring mounted for axial sliding movement on saidtube forward of said first ring; each of said straight line motionlinkages comprising a first link pivotally connected at its inner end tosaid second ring and pivotally connected at its outer end to a set offore and aft petals and a second shorter link pivotally connected at itsinner end to the first ring and pivotally connected at its outer end toan intermediate point of the first link; both of said links beingswingable in a plane containing the axis of the tube and so proportionedand connected that axial movement of the second ring will cause radialmovement of the outer end of the first link substantially in the planeof the throat zone; said means to actuate the linkages including acylinder coaxially mounted in said tube; a piston rod axially movablycarried by said cylinder; a force transfer member carried at the outerfree end of the piston rod; and a plurality of actuator links connectedat one end to the force transfer mechanism and at the other end to thesecond ring.

13. Apparatus as claimed in claim 1; said shroud including a fixedforward section and an aft section axially movably mounted on theforward section; the trailing portion of the aft shroud sectioncomprising a plurality of circumferentially arranged blades, eachconnected at its forward edge to a pivotal mounting on the aft shroudsection for swinging toward and away from the axis of the shroud tomodify the shape of the outer nozzle wall for differing flight regimes;axially movable means adjacent to said pivotal mountings to cause saidblades to swing in unison; force applying means carried by said forwardsection; and variable length force-transmitting means extending betweensaid force-applying means and said axially movable means operable tovary the axial position of the latter in any stage of deployment of theaft section.

14. Apparatus as claimed in claim 1; said shroud including a fixedforward section and an aft section axially movably mounted on theforward section and adapted in its stowed, forward position to cooperatewith the forward section to define said shroud as an elongatesubstantially imperforate conduit; said aft section being movablerearwardly to a deployed position in which at least part of its forwardend is spaced rearwardly from the corresponding part of the rearward endof the fixed section to define said lateral flow path means through thewall of the shroud; the means to coact with the expanded plug comprisinga series of peripherally arranged blocker doors pivotally mounted attheir forward ends to the inner wall of the aft shroud section andswingable inwardly to positions in which their inner ends are insubstantial adjacency with the surface of the expanding plug; a drivelink pivotally connected at its first end to each of said blocker doors;actuating means axially movable with respect to the aft section andconnected to the second end of said drive link to apply force along thelength of said drive link to swing the door to its deployed position.

15. Apparatus as claimed in claim 14; said drive link and actuatingmeans being so arranged with respect to the door that the force of theexhaust gas stream on the door will force the door and the aft shroudsection toward stowed position in the event of failure of the aftsection deploying means.

16. Apparatus as claimed in claim 14; said actuating mean being movablewith the aft shroud section during the first part of its deployingmovement; and stop means to limit the travel of the actuating means andcause it to urge the door to deployed position.

17. Apparatus as claimed in claim 14; track means secured to the forwardshroud section and extending axially rearward into the aft shroudsection; said actuating means comprising an actuating ring slidable onsaid track means; and stop means associated with the track means tolimit rearward movement of the actuating ring.

18. Apparatus as claimed in claim 14; said actuating means being fixedlymounted with respect to the forward shroud section; a pair of togglelinks connected at one end to the actuating means and at the other endto the aft shroud section; an intermediate portion of one of the togglelinks being connected to the second end of said drive link; the relativemovement of the aft section and the actuating means causing folding ofthe toggle links and deployment of the door.

119. Apparatus as claimed in claim 14; said actuating means comprisingan actuating ring located intermediate the ends of the aft shroudsection; an anchorage at the forward end of the aft shroud section; anda pair of toggle links lying in stowed position generally parallel tothe axis of the shroud; the forward toggle link at its free end beingpivotally connected to said anchorage and laterally spaced from thedoor, with its intermediate portion connected to the second end of saiddrive link; the aft toggle link at its free end being pivotallyconnected to the actuating ring; rearward movement of the aft shroudsection with respect to the actuating ring causing folding of the togglelinks and deployment of the door.

20. Apparatus as claimed in claim 19; the arrangement and dimensions ofthe links being chosen to cause gradual opening of the lateral flow pathmeans at a greater rate than the gradual closing of the axial flow pathmeans to prevent any reduction of the total outlet area for emission ofthe exhaust gas stream.

1. Thrust controlling apparatus for use in combination with a jet engine having a rearwardly discharging exhaust outlet or tailpipe, comprising: a shroud carried by said engine and located rearwardly of the exit end of said outlet or tailpipe and coaxial therewith to surround and control the exhaust gas stream issuing from said outlet or tailpipe; and a streamlined diversion plug mounted coaxially within the shroud to define the inner wall of the flow path for the exhaust gas stream; the intermediate portion of the plug being expandable and contractable to vary the flow path area for differing flight regimes; said shroud including means to provide lateral flow path means through its wall and means to coact with the expanded plug to block rearward flow of the exhaust gas stream and redirect it through the lateral flow path means to produce reverse thrust.
 2. Apparatus as claimed in claim 1; said shroud including a fixed forward section and an aft section axially movably mounted on the forward section and adapted in its stowed, forward position to cooperate with the forward section to define said shroud as an elongate substantially imperforate conduit; said aft section being movable rearwardly to a deployed position in which at least part of its forward end is spaced rearwardly from the rearward end of the fixed section to define said lateral flow path means through the wall of the shroud.
 3. Apparatus as claimed in claim 2; the means to coact with the expanded plug comprising a series of peripherally arranged blocked doors pivotally mounted to the inner wall of the aft section of the shroud sand swingable into engagement with the expanded plug; said doors being formed and arranged to completely close the rearward flow path in fully deployed position.
 4. Apparatus as claimed in claim 3; said doors being provided with linkage means adapted to cause their deployment and stowage in response to movement of the aft section tO deployed and stowed positions.
 5. Apparatus as claimed in claim 1; the intermediate portion of said plug comprising a forward cone section diverging rearwardly and an aft cone section diverging forwardly; the bases of said cone sections meeting in a plane transverse to the nozzle axis and defining a throat zone of variable area.
 6. Apparatus as claimed in claim 5; the trailing portion of the aft shroud section comprising a plurality of circumferentially arranged blades, each connected at its forward edge to a pivotal mounting on the aft shroud section; said pivotal mountings, when the aft shroud section is in stowed position, lying in said transverse plane at the throat zone; and means to swing said blades in unison to selected angular positions independent of the condition of expansion of the diversion plug to modify the shape of the outer nozzle wall for differing flight regimes.
 7. Apparatus as claimed in claim 6; the lateral margins of said blades having sealing means in slidable engagement with adjacent blades to produce a substantially imperforate continuation of the outer nozzle wall in all positions of adjustment.
 8. Apparatus as claimed in claim 1; the intermediate portion of said diversion plug comprising a forward cone section diverging rearwardly and an aft cone section diverging forwardly; the bases of said cone sections meeting in a plane transverse to the nozzle axis and defining a throat zone of variable area; a first support member at the forward end of said forward cone section; said forward section comprising a plurality of fore and aft extending elongate petals arranged in laterally overlapping and sliding relation; said petals being pivotally mounted at their forward ends on said first support member; a second support member at the aft end of the aft cone section; said aft section comprising a plurality of petals similar to those of the forward section and pivotally mounted at their aft ends to the second support member; a peripherally arranged series of straight line motion linkages located in the general transverse plane of the throat zone and each having an outer free end movable radially in said plane; the adjacent ends of the petals of the forward and aft cone sections being pivotally connected in pairs to the outer free ends of said linkages to move radially therewith and vary the base diameters of the cone sections; and means to actuate all of said linkages in unison.
 9. Apparatus as claimed in claim 8; said first and second support members being axially movable to provide for changes in the axial lengths of the cone sections in response to changes in their base diameters.
 10. Apparatus as claimed in claim 9; a fixedly mounted tapered nose member extending forwardly ahead of the forward cone section; and a tapered tail member extending rearwardly of the aft cone section and mounted on said second support member for axial movement therewith.
 11. Apparatus as claimed in claim 8; including a plurality of peripherally spaced radially extending struts within said shroud and having their outer ends fixedly secured to the inner wall thereof at its forward end; and elongate support tube arranged coaxially in said shroud and fixedly secured at its forward end to the inner ends of said struts; said support members comprising rings axially slidably mounted on said tube; said straight line motion linkages being mounted on the outer wall of said tube intermediate its ends; said means to actuate said linkages being mounted within said tube; and actuator links connecting said actuating means to said linkages.
 12. Apparatus as claimed in claim 8; including an elongate support tube fixedly mounted coaxially in said shroud; a first ring fixedly mounted on said tube; a second ring mounted for axial sliding movement on said tube forward of said first ring; each of said straight line motion linkages comprising a first link pivotally connected at its inner end to said second ring and pivotally connected at its outer end to a set of fore and aft petalS and a second shorter link pivotally connected at its inner end to the first ring and pivotally connected at its outer end to an intermediate point of the first link; both of said links being swingable in a plane containing the axis of the tube and so proportioned and connected that axial movement of the second ring will cause radial movement of the outer end of the first link substantially in the plane of the throat zone; said means to actuate the linkages including a cylinder coaxially mounted in said tube; a piston rod axially movably carried by said cylinder; a force transfer member carried at the outer free end of the piston rod; and a plurality of actuator links connected at one end to the force transfer mechanism and at the other end to the second ring.
 13. Apparatus as claimed in claim 1; said shroud including a fixed forward section and an aft section axially movably mounted on the forward section; the trailing portion of the aft shroud section comprising a plurality of circumferentially arranged blades, each connected at its forward edge to a pivotal mounting on the aft shroud section for swinging toward and away from the axis of the shroud to modify the shape of the outer nozzle wall for differing flight regimes; axially movable means adjacent to said pivotal mountings to cause said blades to swing in unison; force applying means carried by said forward section; and variable length force-transmitting means extending between said force-applying means and said axially movable means operable to vary the axial position of the latter in any stage of deployment of the aft section.
 14. Apparatus as claimed in claim 1; said shroud including a fixed forward section and an aft section axially movably mounted on the forward section and adapted in its stowed, forward position to cooperate with the forward section to define said shroud as an elongate substantially imperforate conduit; said aft section being movable rearwardly to a deployed position in which at least part of its forward end is spaced rearwardly from the corresponding part of the rearward end of the fixed section to define said lateral flow path means through the wall of the shroud; the means to coact with the expanded plug comprising a series of peripherally arranged blocker doors pivotally mounted at their forward ends to the inner wall of the aft shroud section and swingable inwardly to positions in which their inner ends are in substantial adjacency with the surface of the expanding plug; a drive link pivotally connected at its first end to each of said blocker doors; actuating means axially movable with respect to the aft section and connected to the second end of said drive link to apply force along the length of said drive link to swing the door to its deployed position.
 15. Apparatus as claimed in claim 14; said drive link and actuating means being so arranged with respect to the door that the force of the exhaust gas stream on the door will force the door and the aft shroud section toward stowed position in the event of failure of the aft section deploying means.
 16. Apparatus as claimed in claim 14; said actuating means being movable with the aft shroud section during the first part of its deploying movement; and stop means to limit the travel of the actuating means and cause it to urge the door to deployed position.
 17. Apparatus as claimed in claim 14; track means secured to the forward shroud section and extending axially rearward into the aft shroud section; said actuating means comprising an actuating ring slidable on said track means; and stop means associated with the track means to limit rearward movement of the actuating ring.
 18. Apparatus as claimed in claim 14; said actuating means being fixedly mounted with respect to the forward shroud section; a pair of toggle links connected at one end to the actuating means and at the other end to the aft shroud section; an intermediate portion of one of the toggle links being connected to the second end of said drive link; the relative movEment of the aft section and the actuating means causing folding of the toggle links and deployment of the door.
 19. Apparatus as claimed in claim 14; said actuating means comprising an actuating ring located intermediate the ends of the aft shroud section; an anchorage at the forward end of the aft shroud section; and a pair of toggle links lying in stowed position generally parallel to the axis of the shroud; the forward toggle link at its free end being pivotally connected to said anchorage and laterally spaced from the door, with its intermediate portion connected to the second end of said drive link; the aft toggle link at its free end being pivotally connected to the actuating ring; rearward movement of the aft shroud section with respect to the actuating ring causing folding of the toggle links and deployment of the door.
 20. Apparatus as claimed in claim 19; the arrangement and dimensions of the links being chosen to cause gradual opening of the lateral flow path means at a greater rate than the gradual closing of the axial flow path means to prevent any reduction of the total outlet area for emission of the exhaust gas stream. 